1. Field of the Invention
The present invention relates to communication between systems using a similar mode of communication, and a main object of the present invention is to provide a method of synchronizing (i.e., resolving contention between) two or more interfaces using the same communication resource.
2. Description of the Prior Art
Many transmission systems and communication devices are constructed around or connected to a plurality of send-receive interfaces for setting up unidirectional or bidirectional communication links or transmission connections with one or more other devices, stations or systems, possibly organized in the form of networks.
In some systems and devices the interfaces are obliged to share the same communication means or the same communication resource. This is the case in particular if the interfaces are all “air” interfaces or radiocommunication interfaces.
To prevent interaction or interference between the various interfaces, which would be harmful to the connections or links incorporating them, it is then necessary to ensure compatible use of the shared means or resource, in terms of access, efficient use and release.
The most obvious solution to the problem of ensuring compatible use, and the one that is the easiest to implement, entails the use of interfaces co-existing and operating independently of each other.
In the case of a system or device comprising a plurality of air interfaces it is necessary to ensure mutual electromagnetic compatibility at all times of the interfaces obliged to use the shared radio resource.
At present compatibility is achieved either by using different frequency bands at the various interfaces, which are sufficiently far apart in the radio spectrum to authorize simultaneous sending/receiving by the interfaces, or by designing the interfaces so that any interaction or interference caused by the other interfaces is attenuated or filtered.
However, these existing solutions are not satisfactory and all have significant limitations and/or drawbacks.
Using frequency bands that are far apart raises the problem of the availability of bands satisfying the applicable criteria appropriate to the interfaces concerned, and in fact leads to the creation of multiple resources (one for each interface), each frequency band having to be considered as a separate radio resource, rather than sharing a shared resource.
What is more, the additional cost of reciprocal filtering of interference between the various interfaces can be high and incompatible with products intended for private individuals or consumers, for example base stations of CTS local area networks integrating an interface to a microwave public telecommunication network.
What is more, given their composition and/or their mode of operation, some communication systems or devices are unable to support independent ports, or to allow independent use of a shared resource by a plurality of separate interfaces.
A particular object of the present invention is to alleviate the above drawbacks.